Expanding wetland mitigation: Can rice fields remediate pesticides in agricultural runoff?

Authors: Moore, Matthew; Locke, Martin; CULLUM, ROBERT - Retired ARS Employee

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/27/2018
Publication Date: 9/13/2018
Citation: Moore, M.T., Locke, M.A., Cullum, R.T. 2018. Expanding wetland mitigation: Can rice fields remediate pesticides in agricultural runoff? Journal of Environmental Quality. 47:1564-1571. https://doi.org/10.2134/jeq2018.04.0154.
DOI: https://doi.org/10.2134/jeq2018.04.0154

Interpretive Summary: Pesticides in agricultural runoff can cause significant damage to rivers, lakes, and streams. Innovative management practices are needed at edge-of-field to reduce the potential impact of pesticides to water bodies. Mesocosm experiments at the University of Mississippi Field Station demonstrated that contaminated water flowing through systems planted with rice resulted in significant reductions of two pesticides--atrazine and diazinon. Using rice for phytoremediation has the potential to address water quality concerns in developing countries that depend on the crop for their food supply. However, more research must be conducted on potential contaminant transfer to seed before moving toward large scale implementation.

Technical Abstract: Pesticides are responsible for over 1,800 water quality impairments in the United States. Impacts of pesticide runoff on aquatic ecosystems can be mitigated by implementing management practices such as constructed wetlands, grass buffers, and vegetated ditches. A new method currently being examined is the use of rice fields for phytoremediation of pesticide-contaminated water. Rice (Oryza sativa) is cultivated on every continent except Antarctica and is the staple food crop of 20% of the world’s population. Four, 0.01 ha fields (two planted with rice, two left bare) were amended with a mixture of atrazine, diazinon, and permethrin during a one-time storm event, and pesticide concentrations and loads were monitored in water, sediment, and plant samples. The experiment was repeated the following year. Significant differences were noted for mitigation of atrazine and diazinon loads in rice versus bare systems. Overall, atrazine loads in the water of rice systems decreased 85±8% from inflow to outflow, while atrazine loads in the water of bare systems decreased 58±7%. Similar patterns were seen for diazinon (86±4% versus 62±7%), cis-permethrin (94±2% versus 64±12%), and trans-permethrin (97±2% versus 67±14%). All three pesticides were found repeatedly sorbed to plant material in the inflow and outflow areas during the first year, while the second year resulted in much less plant-pesticide contribution to overall mitigation. Further investigation is needed to compare rice’s mitigation capacity of different pesticide classes, as well as potential transfer of pesticides to edible seeds.